The first thought-activated implant is an exciting hint of things to come

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The main achievement in optogenetics, at least so far, has been the reliable activation of neurons using light. In recent years that concept has been taken a step further with the ability to activate specific genes within those neurons using light. Researchers led by Martin Fussenegger from ETH Zürich have now implanted a living mouse with designer cells bearing genes that can be precisely controlled with light. As we will describe, that is technically challenging enough. But it is what they did next — namely, for a human wearing a brain-computer interface to remotely control the rat’s brain implant with thoughts alone — that has people talking.

The hardware pipeline they used by ETH Zurich was fairly low tech (relatively speaking, anyway). An EEG cap worn by the human picks up crude signals that reflect the general meditative state of the subject, i.e. relaxed vs less relaxed. After some signal processing, a coil almost identical to what you might find in a wireless charger is energized with a current that more-or-less varies according to that signal. The mouse, which has the implant containing the special cells which contain the special genes, sits over this coil basking in the glow of its electromagnetic field. The implant also has the receiver — basically just three orthogonal secondary coils (presumably so that some energy is intercepted regardless of the mouse’s orientation) along with a few capacitors to tune them, and a few diodes to rectify the received power so that a small DC voltage is obtained. This voltage controls a blue LED, which in turn illuminates the optogenetically enhanced cells in the implant.

That all may sound cool, but it’s something any kid with a soldering iron and enough smarts to construct a crystal radio set could handle. It’s the opto-enhanced part that would probably require a bit more support from a fairly sophisticated DIY genetics lab. The cells used are known as HEK cells, for human embryonic kidney cells. Kidney cells are generally not too exciting, although these particular fellows are now fairly omnipotent creatures by virtue of the handy genetic toolkits that have been developed for them. The cells have many of the same properties of immature neurons and can impersonate many more — not least of which being the adrenal cells that sit atop the kidney and dump grams of adrenalin into the blood during video games.

The list of all things that the researchers then did to these cells — the viral vectors, plasmids, and other elements engineered into them — takes up two pages in the supplementary methods so mercifully we won’t detail all of them here. [Research paper: doi:10.1038/ncomms6392]

One day, you’ll have a mind-controlled brain implant

The main goal the researchers had was to be able to close a physiologic loop from (in this case meditative) thought to metabolic control. Here the mouse acted as a proxy for the full loop that will one day reside in a single person — or, we can only suppose, in two or more appropriately synchronized persons. The way we know that it worked was because when the subject had the right thought, the gene in the mouse that encodes an enzyme called SEAP (secreted placental alkaline phosphatase) got activated. This gene was chosen because once it is activated, it manufactures the SEAP enzyme and then secretes it into the bloodstream where the researchers then measured it. In addition, alkaline phosphate naturally or unnaturally found in the blood is commonly used to asses disease state of various organs and there are several are easy ways to detect it.

Unfortunately, things are not quite as simple as we have described so far because blue light from the LED doesn’t activate the gene directly. The researchers actually used a light-responsive bacterial protein called DGCL for that. Believe it or not, there were several other synthetic protein links that had to be made just to get from DGCL to SEAP but that is left as an exercise for those who want to dig in. It is fairly remarkable that any kind of linear response from thought to enzyme level could be preserved through such an intricate electro-molecular chain. Hopefully this kind of technology will be increasingly embraced by a new breed of electrical-genetic engineers who are comfortable in the language of both fields. That way the most sensible ways to proceed on both fronts might be insured.

Thanks to the advances here, you might one day have a mind-controlled implant in your brain; you’ll be able to think about something — perhaps you want an additional dose of adrenaline or dopamine — and the implant will then dutifully trigger the release of the desired hormones.

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